U.S. Pat. No. 4,809,814 dated Mar. 7, 1989, entitled: SCAFFOLDING, inventor Jean St-Germain, describes a scaffolding including a pair of towers each made of tower sections adapted to be secured in end-to-end relation, a work platform completely surrounding said towers and hydraulically-operated hooks extendable and retractable along the towers and selectively engaging steps of said towers to raise the platform along the towers. Although the work platform assembly in accordance with the above-noted invention has been found to be a great improvement over conventional manually-erected scaffoldings, certain inconveniences have been found in practice, such as the need to climb down the platform onto a suspended swing stage for the installation of cross-braces interconnecting the towers and of anchors to secure the towers to the building wall, these operations being effected every time the platform is raised a certain amount. The removal of the braces and of the anchors needs also to be effected in the same manner every time the platform is lowered.
A further disadvantage of the scaffolding of this prior patent resides in the fact that several work platforms cannot be suspended at different levels from the main work platform due to the existence of the cross-braces, thereby restricting concurrently effected work at a single level, namely the platform level.
Another disadvantage of the above-noted system resides in the fact that the hydraulically-operated platform raising means is an expensive raising mechanism which also entails frequent maintenance due to the working environment in which it is located.
Another disadvantage of the system is that for each platform, two columns or towers are required, resulting in a time-consuming and expensive installation for a given platform length.